3 Part One. The Predicate

Solubility
While there are many pairs of substances which, like water and ethyl alcohol, can be mixed in any proportions to form homogeneous solutions, it is a matter of common experience that the capacity of a solvent to dissolve a given solute is often limited. When a solvent placed in contact with an excess o f solute attains and maintains a constant concentration of solute, the solute and solution are at equilibrium, and the solution is said to be saturated. The solubility of a substance in a particular solvent at a given temperature is the concentration of the solute in the saturated solution. In other words, the solubility of a solute is the dissolved concentration characteristic of the state of equilibrium between the solute and the solution.

It is difficult to overemphasize the importance of the concept of solubility to chemistry; it is the basis of innumerable laboratory and industrial processes that prepare, separate, and purify chemicals, and is the controlling factor in a variety of geological and other natural phenomena. The solubility of a substance in a particular solvent is controlled principally by the nature of the solvent and solute themselves, but also by the conditions of temperature and pressure. To analyse these factors, We shall first limit ourselves to the ease of ideal solutions.

The liquids (hai form an ideal solution are always misciblc in any proportions and, thus, have infinite solubility in cach other. The reason for this is easy to see if We recall two facts. First, limited solubility and a saturated solution result only when a solute and its solution reach equilibrium. Second, the equilibrium state is a compromise between a natural tcndcncy toward minimum energy and maximum molecular chaos.

Now, the mixing of two ideal liquids is always accompanied by an increase in entropy or molecular chaos, because in the solution, the solute molecules are spread randomly throughout the solvent, rather than being nearly closest packed as they are in the pure solute. That is, even if We could locate one solute molecule in solution, We could not predict what the identity of its nearest neighbours was, as We could, if the molecule were in the pure solute phase. Consequently, the solution has a higher entropy than the pure solvent and solute, and the tcndcncy toward maximum molecular chaos favours the mixing o f the two liquids.

Moreover, the fact that there is no energy changc in the mixing process means that the tcndcncy toward minimum energy does not restrict the solution process. Consequently, the two liquid components o f an ideal solution can mix in any proportion.
Words and Word-Combinations to Be Memorized

as is the case with, as the case may be, in case, in which case, it is far from the ease, it is not the case with, such is the ease, a chemical, contact, emphasize, excess, experience, be a matter of common experience, favour, ideal, identity, maintain, maximum, natural, purify, result, saturate, saturated, solubility, spread, themselves, toward(s), a variety of

Ex. 5. Give the Uzbek equivalents for the following:

mix in any proportions, the capacity to dissolve a solute, place in contact with, the solubility in a particular solvent, purify chemicals, be a controlling factor, a variety of phenomena, be controlled by the nature of the solvent and solute, be misciblc in any proportions, be spread randomly throughout the solvent, be close packcd, moreover, restrict the process, emphasize the importance

Ex. 6. Give the English equivalents for the following:

Tajribadan ma'lumki, cheklangan qobiliyat, eriydigan moddaning haddan tashqari ko'tarilishi, muvozanatda bo'lish, ma'lum harorat va bosimda to'yingan eritmada bo'lish, boshqacha aytganda, kimyo uchun eruvchanlik kontseptsiyasining ahamiyati, ko'plab tabiiy hodisalarda, vaziyat bilan cheklanib qolish, ideal echim topish, muvozanatga erishish, haroratning oshishi bilan birga keladi, ammo ... energiya o'zgarmasa ham

Ex. 7. Fill in (he blanks with articles where necessary.

1. Substances like ... water and ... ethyl alcohol can be mixed in any proportions. 2. ... capacity o f ... solvent to dissolve ... given solute is often limited. 3 .... solubility o f ... substance in ... particular solvent at ... given temperature is its concentration in ... saturated solution. 4. It is difficult to overemphasize... importance o f ... concept o f ... solubility to ... chemistry. 5. We shall first analyse... case o f ... ideal solution.

Ex. 8. Give synonyms for the following:

capacity, limit, place, principally, be accompanied by, because, toward, consequently

Ex. 9. Give antonyms for the following:

constant, saturated, at first, always, easy, decrease, near, minimum, seldom, limited

Ex. 10. Translate the sentences into Uzbek.

1. The capacity of a solvent to dissolve a given solute is often limited though there are many pairs of substances which can be mixed in any proportions. 2. In order to control our environment, the first purpose of science must be to study and understand it. 3. To answer the question “What are the uses of sulphuric acid?” fully, one would need to write a book. 4. The alkali metals are usually stored in oil so as to cxcludc air.5. In order for two molecules to react with each other, they must, first of all, be in the prcsencc o f each other. 6. For hydrogen to be obtained from water, electrolysis may be used. 7. Sodium is a white metal soft enough to be easily cut with a knife and light enough to float on water. 8. The minerals in which aluminium occurs, are too numerous to recite. 9. The vapour pressure of many pure liquids or solids is very low, in fact, so low as to be immeasurable by direct means. 10. The catalytic substance can be recovered unchanged after the reaction is completed. 11. As the temperature is raised, the rate of evaporation increases. 12. Oncc the validity of a hypothesis has been tested by all possible experiments and is found to be in harmony with all the facts, it assumes the status of a theory. 13. Whenever a chemical reaction occurs, an energy changc takes place. 14. Liquid bromine should be kept in well-stopped bottles, as this clement is poisonous. 15. The discovery of silicon was an important event in chemistiy, for the properties of the clement were found to be very close to those predicted by D. I. Mendeleyev on the basis of his periodic law. 16. Where the current enters or leaves the liquid, there are evidences of chemical action having taken place. 17. If sulphur trioxidc is thrown into water, it will dissolve with the evolution of much heat. 18. If there were no order in the way in which atoms of different elements combine to form the molecules and crystals of compounds, it would be necessary for us to memorize one by one the formulas of thousands of substances. 19. If We had chosen the second oxide, the valence of sulphur and, therefore, its equivalent weight would have been different. 20. With a few exceptions the molten metals are completely soluble in one another, so that it is possible to make solutions of all concentrations. 21. True salts are always ionic, whether they are in solution or in their crystalline forms. 22. Fluorine and hydrogen combinc violently even in the dark, provided a trace of moisture is present.23. Strange as it may seem, the reaction may procccd both ways.24. Important as the problem of solubility may be, We shall not consider it now. 25. Let us consider any factors lest anything may be omitted. 26. Unless the electron microscopc had been used, it would not have been possible to obtain these results. 27. Were the parameters maintained, the reaction would go to completion. 28. Physics and chemistry are so closely related that textbooks of these two subjects contain much in common.29. Many oxides are found to combinc with acids to form salts and water.30. Carbon monoxide cannot properly be described as cither a basic or an acidic oxide, inasmuch as it does not react with water.
Ex. 11. Translate the sentences into English without using a dictionary.

1. Turli xil moddalar bir erituvchida turli xil eruvchanlikka ega. 2. Moddaning eruvchanligi bu uning konsentratsiyasi, eriydigan modda va eritma o'rtasidagi muvozanat holatining tavsifi. 3. Eruvchanlik tushunchasi ko'plab laboratoriya va ishlab chiqarish jarayonlari uchun asosdir. 4. Eruvchanlik erituvchining o'zi va erituvchisi xususiyatiga ham, jarayon sharoitlariga ham bog'liq. 5. Ideal eritmaning ikkita suyuq tarkibiy qismini har qanday nisbatda aralashtirish mumkin.

Ex. 12. Answer the following questions:

1. In what way can the capacity of a solvent to dissolve a given solute be characterized? 2. What state is regarded as equilibrium between the a solute and solution? 3. What is usually called the solubility of a substance in a particular solvent? 4. What is the importance o f the concept of solubility? 5. What is an ideal solution?